EP0464176B1 - Liquid crystalline medium - Google Patents

Abstract

A liquid crystalline medium based on a mixture of moderately polar compounds contains one or more compounds of general formula (I), where the individual residues have the following meanings: R stands for alkyl, oxalkyl, fluoralkyl or alkenyl, each of which has up to 7 carbon atoms, (a) stands for (b), (c) or (d), X stands for F, Cl, CF3, OCHF2, OCF2Cl or OCF3, and Y stands for H or F.

Description

The present invention relates to a liquid-crystalline medium, its use for electro-optical purposes and displays containing this medium.

Liquid crystals are mainly used as dielectrics in display devices, since the optical properties of such substances can be influenced by an applied voltage. Electro-optical devices based on liquid crystals are well known to the person skilled in the art and can be based on various effects. Such devices are, for example, cells with dynamic scattering, DAP cells (deformation of aligned phases), guest / host cells, TN cells with a twisted nematic ("twisted nematic") structure, STN cells ("super-twisted nematic"), SBE cells ("super birefringence effect") and OMI cells ("optical mode interference"). The most common display devices are based on the Schadt-Helfrich effect and have a twisted nematic structure.

The liquid crystal materials must have good chemical and thermal stability and good stability against electric fields and electromagnetic radiation. Furthermore, the liquid crystal materials have low viscosity and result in short response times, low threshold voltages and high contrast in the cells. Furthermore, they should have a suitable mesophase at the usual operating temperatures, ie in the widest possible range below and above room temperature, for example a nematic or cholesteric mesophase for the above-mentioned cells. Since liquid crystals are generally used as mixtures of several components, it is important that the components are readily miscible with one another. Other properties, such as electrical conductivity, dielectric anisotropy and optical anisotropy, must meet different requirements depending on the cell type and area of application. For example, materials for cells with a twisted nematic structure should have positive dielectric anisotropy and low electrical conductivity.

For example, for matrix liquid crystal displays with integrated non-linear elements for switching individual pixels (MLC displays), media with large positive dielectric anisotropy, wide nematic phases, relatively low birefringence, very high specific resistance, good UV and temperature stability of the resistance and low Vapor pressure desired.

• 1. MOS (Metal Oxide Semiconductor)-Transistoren auf Silizium-Wafer als Substrat.
• 2. Dünnfilm-Transistoren (TFT) auf einer Glasplatte als Substrat.

Matrix liquid crystal displays according to the preamble are known. For example, active elements (ie transistors) can be used as non-linear elements for the individual switching of the individual pixels. One speaks then of an "active matrix", whereby one can distinguish two types:

• 1. MOS (Metal Oxide Semiconductor) transistors on silicon wafers as substrates.
• 2. Thin film transistors (TFT) on a glass plate as a substrate.

• (a) two-terminal devices (diode ring)
• (b) three-terminal devices (TFT)

Die Verwendung von einkristallinem Silizium als Substratmaterial beschränkt die Displaygröße, da auch die modulartige Zusammensetzung verschiedener Teildisplays an den Stößen zu Problemen führt.Another categorization is:

• (a) two-terminal devices (diode ring)
• (b) three-terminal devices (TFT)

The use of monocrystalline silicon as substrate material limits the size of the display, since the modular composition of various partial displays at the joints also leads to problems.

With the more promising type 2, which is preferred, the TN effect is usually used as the electro-optical effect. There are two technologies: TFTs made of compound semiconductors such as CdSe or TFT's based on polycrystalline or amorphous silicon. The latter technology is being worked on with great intensity worldwide.

The TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries the transparent counter electrode on the inside. Compared to the size of the pixel electrode, the TFT is very small and practically does not disturb the image. This technology can also be expanded for fully color-compatible image representations, a mosaic of red, green and blue filters being arranged in such a way that a filter element is located opposite a switchable image element.

The TFT displays usually work as TN cells with crossed polarizers in transmission and are illuminated from behind.

The term MLC displays here encompasses any matrix display with integrated non-linear elements, i.e. in addition to the active matrix, displays with passive elements such as varistors or diodes (MIM = metal-insulator-metal).

MLC displays of this type are particularly suitable for TV applications (for example pocket TVs) or for high-information displays for computer applications (laptops) and in automobile or aircraft construction. In addition to problems with the angle dependence of the contrast and the switching times, difficulties arise with MLC displays due to the insufficiently high specific resistance of the liquid crystal mixtures [TOGASHI` S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMAXI, K. , TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, Sept. 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, p. 141 ff, Paris; STROMER, M., Proc. Eurodisplay 84, Sept. 1984: Design of Thin Film Transistors for Matrix Adressing of Television Liquid Crystal Displays, p. 145 ff, Paris]. With decreasing resistance, the contrast of an MLC display deteriorates and the problem of "after image elimination" can occur. Since the resistivity of the liquid crystal mixture generally decreases over the lifetime of an MLC display due to interaction with the inner surfaces of the display, a high (initial) resistance is very important in order to obtain acceptable service lives. Especially with low-voltage mixtures (threshold voltage V₁₀ ≦ 1.5 volts, clearing point ≧ 65 ° C), it was previously not possible to realize very high resistivities. It is also important that the specific resistance increase as little as possible with increasing Shows temperature as well as after temperature and / or UV exposure. The state-of-the-art MFK displays do not meet today's requirements.

There is therefore still a great need for MLC displays with a very high specific resistance combined with a large working temperature range, short switching times and low threshold voltage, which do not show these disadvantages or only show them to a lesser extent.

The object of the invention is to provide media, in particular for such MFK displays, which do not have the disadvantages indicated above or only to a lesser extent, at the same time have very high resistivities and low threshold voltages.

It has now been found that this object can be achieved if media according to the invention are used in these MLC displays.

enthält, worin die einzelnen Reste die folgenden Bedeutungen haben:

R

Alkyl, Oxaalkyl, Flüoralkyl oder Alkenyl mit jeweils bis zu 7 C-Atomen bedeutet,

X

F, Cl, OCHF₂, OCF₂Cl oder OCF₃,

Y

H oder F,

und zusätzlich eine oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln II, III und IV und/oder V bis VIII enthält

worin R, X und Y jeweils unabhängig voneinander eine der für Formel I angegebenen Bedeutung haben, wobei Medien enthaltend Verbindungen der Formel

worin R¹ und R² jeweils unabhängig voneinander n-Alkyl, ω-Fluoralkyl oder n-Alkenyl mit bis zu 9 C-Atomen bedeuten, ausgeschlossen sind.The invention thus relates to a liquid-crystalline medium based on a mixture of medium-polar compounds, characterized in that it contains one or more compounds of the general formula I.

contains, in which the individual radicals have the following meanings:

R

Means alkyl, oxaalkyl, fluoroalkyl or alkenyl, each with up to 7 carbon atoms,

X

F, Cl, OCHF₂, OCF₂Cl or OCF₃,

Y

H or F,

and additionally contains one or more compounds selected from the group consisting of the general formulas II, III and IV and / or V to VIII

wherein R, X and Y each independently have one of the meanings given for formula I, media comprising compounds of the formula

wherein R¹ and R² each independently of the other denote n-alkyl, ω-fluoroalkyl or n-alkenyl with up to 9 carbon atoms.

The invention also relates to electro-optical displays (in particular STN or MFK displays with two plane-parallel carrier plates which form a cell with a border, integrated non-linear elements for switching individual pixels on the carrier plates and a nematic liquid crystal mixture in the cell with a positive one dielectric anisotropy and high resistivity) containing such media and the use of these media for electro-optical purposes.

Similar liquid-crystalline media containing pyrimidine derivatives are known from EP-A-0 258 868 and EP-A-0 123 907. Similar media with heterocyclic derivatives with a trifluoromethylphenyl radical are described in WO 87/06602. Finally, other similar media are described in documents JP 60-163 991, EP-A-0 395 220 and WO 90/04623.

The liquid crystal mixtures according to the invention make it possible at the same time to achieve threshold voltages preferably ≦ 1.65 volts, clearing points above 60 °, preferably above 65 ° and / or a high value for the specific resistance at low viscosities, as a result of which excellent MKF displays can be achieved. It goes without saying that through a suitable choice of the components of the mixtures according to the invention, higher clearing points (eg above 90 °) at higher threshold voltages (V _th <2.2 volts) while maintaining the other advantageous Properties can be realized. The MFK displays according to the invention preferably operate in the first transmission minimum according to Gooch and Tarry [CH Gooch and HA Tarry, Electron. Lett. 10, 2-4, 1974; CH Gooch and HA Tarry, Appl. Phys., Vol. 8, 1575-1584, 1975], where in addition to particularly favorable electro-optical properties such as high slope of the characteristic and low angle dependence of the contrast (DE-PS 30 22 818) with the same threshold voltage as in an analog display in the second At least a smaller dielectric anisotropy is sufficient. As a result, significantly higher specific resistances can be achieved using the mixtures according to the invention in the first minimum. The person skilled in the art can set the birefringence required for a given layer thickness of the MLC display by means of suitable routine selection of the individual components and their proportions by weight.

Auch die UV-Stabilität der erfindungegemäßen Mischungen ist erheblich besser, d. h. sie zeigen eine deutlich kleinere Abnahme des HR unter UV-Belastung.Capacity Holding Ration (HR) Measurements [p. Matsumoto et al., Liquid Crystals 5 , 1320 (1989); K. Niwa et al., Proc. SID Conference, San Francisco, June 1984, p. 304 (1984); G. Weber et al., Liquid Crystals 5 , 1381 (1989)] have shown that mixtures according to the invention containing compounds of the formula I have a significantly smaller decrease in HR with increasing temperature than analogous mixtures containing instead of the compounds of the formula I cyanophenylcyclohexanes of the formula

The UV stability of the mixtures according to the invention is also considerably better, ie they show a significantly smaller decrease in HR under UV exposure.

The viscosity at 20 ° C is preferably ≦ 25 mPa.s. The nematic phase range is preferably at least 70 °, in particular at least 80 °. This range preferably extends at least from -20 ° to + 70 °.

The individual compounds of the formulas 1 to XII and their sub-formulas which can be used in the MLC displays according to the invention are either known, or they can be prepared analogously to the known compounds.

• Medium enthält eine oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln II, III und IV:
  
  worin R, X und Y jeweils unabhängig voneinander eine der in Anspruch 1 angegebene Bedeutung haben.
• Medium enthält eine oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln V bis VIII:
  
  worin R, X und Y jeweils unabhängig voneinander eine der in Anspruch 1 angegebene Bedeutung haben.
• Medium enthält zusätzlich eine oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus der allgemeinen Formeln IX bis XII:
  
  
  worin R, X und Y jeweils unabhängig voneinander eine der in Anspruch 1 angegebene Bedeutung haben.
• Der Anteil an Verbindungen der Formeln I bis IV zusammen beträgt im Gesamtgemisch mindestens 50 Gew.-%
• der Anteil an Verbindungen der Formel I beträgt im Gesamtgemisch 10 bis 50 Gew.-%
• der Anteil an Verbindungen der Formeln II bis IV im Gesamtgemisch beträgt 40 bis 90 Gew.-% (vorzugsweise 50-70 Gew.-%)
• Y in Formel I ist H
• 
• X ist OCF₃, F oder Cl
• X ist OCF₂H
• das Medium enthält Verbindungen der Formeln II und III oder IV
• R ist geradkettiges Alkyl oder Alkenyl mit 2 bis 7 C-Atomen
• das Medium besteht im wesentlichen aus Verbindungen der Formeln I bis IV
• das Medium enthält weitere Verbindungen, vorzugsweise ausgewählt aus der folgenden Gruppe:
  
  
• Das Gewichtsverhältnis I: (II + III + IV) ist vorzugsweise 1 : 4 bis 1 : 1.
• Medium besteht im wesentlichen aus aus Verbindungen ausgewählt aus der Gruppe bestehend aus den allgemeinen Formeln I bis XII.
• Medium enthält eine oder mehrere Verbindungen der Formel I2, I3 und/oder I4:
  
  worin R die angegebene Bedeutung hat, Q CH, Z F, Cl oder H und Y H oder F bedeutet.

Preferred embodiments are given below:

• Medium contains one or more compounds selected from the group consisting of the general formulas II, III and IV:
  
  wherein R, X and Y each independently have one of the meanings given in claim 1.
• Medium contains one or more compounds selected from the group consisting of the general formulas V to VIII:
  
  wherein R, X and Y each independently have one of the meanings given in claim 1.
• Medium additionally contains one or more compounds selected from the group consisting of the general formulas IX to XII:
  
  
  wherein R, X and Y each independently have one of the meanings given in claim 1.
• The proportion of compounds of the formulas I to IV together is at least 50% by weight in the mixture as a whole.
• the proportion of compounds of the formula I in the total mixture is 10 to 50% by weight
• the proportion of compounds of the formulas II to IV in the mixture as a whole is 40 to 90% by weight (preferably 50-70% by weight)
• Y in Formula I is H
• 
• X is OCF₃, F or Cl
• X is OCF₂H
• the medium contains compounds of the formulas II and III or IV
• R is straight-chain alkyl or alkenyl with 2 to 7 carbon atoms
• the medium consists essentially of compounds of the formulas I to IV
• the medium contains further compounds, preferably selected from the following group:
  
  
• The weight ratio I: (II + III + IV) is preferably 1: 4 to 1: 1.
• Medium essentially consists of compounds selected from the group consisting of the general formulas I to XII.
• Medium contains one or more compounds of the formula I2, I3 and / or I4:
  
  wherein R has the meaning given, Q is CH, ZF, Cl or H and YH or F.

It has been found that a relatively small proportion of compounds of the formula I in admixture with one or more compounds of the formula II, III and / or IV leads to a considerable improvement in the response times and to low threshold voltages, with wide nematic phases with deep ones Transition temperatures can be observed smectically-nematically. The compounds of the formulas I to IV are colorless, stable and readily miscible with one another and with other liquid crystal materials.

The term "alkyl" encompasses straight-chain and branched alkyl groups having 1-7 carbon atoms, in particular the straight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups with 2-5 carbon atoms are generally preferred.

The term "alkenyl" encompasses straight-chain and branched alkenyl groups having 2-7 carbon atoms, in particular the straight-chain groups. Alkenyl groups in particular are C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl, C₅-C₇-4-alkenyl, C₆-C₇-5-alkenyl and C₇-6-alkenyl, in particular C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl and C₅-C₇-4-alkenyl. Examples of preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups of up to 5 carbon atoms are generally preferred.

The term "fluoroalkyl" preferably encompasses straight chain groups with terminal fluorine, i.e. Fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorhexyl and 7-fluoroheptyl. However, other positions of the fluorine are not excluded.

The term "oxaalkyl" preferably includes straight-chain radicals of the formula C _n H _{2n + 1} -O- (CH₂) _m , in which n and m each independently represent 1 to 6. Preferably n = 1 and m is 1 to 6.

The response times, the threshold voltage, the steepness of the transmission characteristics, etc. can be modified in a desired manner by a suitable choice of the meanings of R, X and Y. For example, 1E alkenyl, 3E alkenyl, 2E alkenyloxy, and the like typically result in shorter response times, improved nematic tendencies, and one higher ratio of the elastic constants k₃₃ (bend) and k₁₁ (splay) compared to alkyl or alkoxy radicals. 4-alkenyl residues, 3-alkenyl residues and the like generally give lower threshold voltages and smaller values of k₃₃ / k₁₁ compared to alkyl and alkoxy residues. A group -CH₂CH₂- in Z¹ or Z² generally leads to higher values of k₃₃ / k₁₁ compared to a simple covalent bond. Higher values of k₃₃ / k₁₁ enable, for example, flatter transmission characteristics in TH cells with 90 ° twist (to achieve gray tones) and steeper transmission characteristics in STN, SBE and OMI cells (higher multiplexability) and vice versa
The optimal quantitative ratio of the compounds of the formulas I and II + III + IV largely depends on the desired properties, on the choice of the components of the formulas I, II, III and / or IV and on the choice of further components which may be present. Suitable proportions within the range given above can easily be determined from case to case.

The total amount of compounds of the formulas I to XII in the mixtures according to the invention is not critical. The mixtures can therefore contain one or more further components in order to optimize various properties. However, the observed effect on the response times and the threshold voltage is generally greater the higher the total concentration of compounds of the formulas I to XII.

(X ist vorzugsweise F oder Cl, insbesondere F.)The mixtures according to the invention preferably contain one or more compounds of the formula Ia. The total amount of compounds of the formula Ia in the mixture is preferably at least 10% by weight, particularly preferably at least 15% by weight

(X is preferably F or Cl, especially F.)

Die erfindungsgemäßen Gemische enthalten vorzugsweise eine oder mehrere Verbindungen der Formel Ie. Die Gesamtmenge an Verbindungen der Formel Ie im Gemisch beträgt vorzugsweise mindestens 10 Gew.-%, besonders bevorzugt mindestens 15 Gew.-%.

Die erfindungsgemäßen Medien können ferner eine Komponente A enthalten bestehend aus einer oder mehreren Verbindungen mit einer dielektrischen Anisotropie von -1,5 bis +1,5 der allgemeinen Formel I'

worin

R¹ und R²

jeweils unabhängig voneinander n-Alkyl, ω-Fluoralkyl oder n-Alkenyl mit bis zu 9 C-Atomen,

die Ringe A¹, A² und A³

jeweils unabhängig voneinander 1,4-Phenylen, 2- oder 3-Fluor-1,4-phenylen, trans-1,4-Cyclohexylen oder 1,4-Cyclohexenylen,

Z¹ und Z²

jeweils unabhängig voneinander -CH₂CH₂-oder eine Einfachbindung,

und

m

0, 1 oder 2 bedeutet.

The mixtures according to the invention preferably contain one or more compounds of the formula Ic.

The mixtures according to the invention preferably contain one or more compounds of the formula Ie. The total amount of compounds of the formula Ie in the mixture is preferably at least 10% by weight, particularly preferably at least 15% by weight.

The media according to the invention can also contain a component A consisting of one or more compounds having a dielectric anisotropy of -1.5 to +1.5 of the general formula I '

wherein

R1 and R2

each independently of one another n-alkyl, ω-fluoroalkyl or n-alkenyl with up to 9 C atoms,

the rings A¹, A² and A³

each independently 1,4-phenylene, 2- or 3-fluoro-1,4-phenylene, trans-1,4-cyclohexylene or 1,4-cyclohexenylene,

Z¹ and Z²

each independently of one another -CH₂CH₂-or a single bond,

and

m

0, 1 or 2 means.

worin R¹ und R² die bei Formel I' angegebene Bedeutung haben. Vorzugsweise enthält Komponente A zusätzlich eine oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus II8 bis II20:

worin R¹ und R² die bei Formel I' angegebene Bedeutung haben und die 1,4-Phenylengruppen in II8 bis II17 jeweils unabhängig voneinander auch durch Fluor ein- oder mehrfach substituiert sein können.Component A preferably contains one or more compounds selected from the group consisting of II1 to II7:

wherein R¹ and R² have the meaning given for formula I '. Component A preferably additionally contains one or more compounds selected from the group consisting of II8 to II20:

wherein R¹ and R² have the meaning given in formula I 'and the 1,4-phenylene groups in II8 to II17 can each be substituted independently or independently by fluorine.

worin R¹ und R² die bei Formel I' angegebene Bedeutung haben und die 1,4-Phenylengruppen in II21 bis II25 jeweils unabhängig voneinander auch durch Fluor ein- oder mehrfach substituiert sein können.Component A also preferably additionally contains one or more compounds selected from the group consisting of II21 to II25:

wherein R¹ and R² have the meaning given in formula I 'and the 1,4-phenylene groups in II21 to II25 can each be substituted independently or independently by fluorine.

worin C_rH_2r+1 eine geradkettige Alkylgruppe mit bis zu 7 C-Atomen ist.Finally, mixtures of this type are preferred whose component A contains one or more compounds selected from the group consisting of II26 and II27:

wherein C _r H _{2r + 1 is} a straight-chain alkyl group with up to 7 C atoms.

worin

R¹ und R²

die bei Formel I' angegebene Bedeutung haben

und

Z⁰

eine Einfachbindung, -CH₂CH₂-,

bedeutet,
zur Unterdrückung smektischer Phasen als vorteilhaft, obwohl hierdurch der spezifische Widerstand erniedrigt werden kann. Zur Erzielung von für die Anwendung optimaler Parameterkombinationen kann der Fachmann leicht feststellen, ob und falls ja in welcher Menge diese Verbindungen zugesetzt sein können. Normalerweise werden weniger als 15 %, insbesondere 5-10 % verwendet.In some cases the addition of compounds of the formula proves to be

wherein

R1 and R2

have the meaning given in formula I '

and

Z⁰

a single bond, -CH₂CH₂-,

means
to suppress smectic phases as advantageous, although this can lower the specific resistance. In order to achieve optimal combinations of parameters for the application, the person skilled in the art can easily determine whether and if so in what amount these compounds can be added. Usually less than 15%, especially 5-10% is used.

worin R¹ und R² die bei Formel I' angegebene Bedeutung haben.Also preferred are liquid crystal mixtures which contain one or more compounds selected from the group consisting of III 'and IV':

wherein R¹ and R² have the meaning given for formula I '.

The construction of the MFK display according to the invention from polarizers, electrode base plates and electrodes with surface treatment corresponds to the design customary for such displays. The term conventional construction is broadly encompassed here and also includes all modifications and modifications of the MLC display, in particular also matrix display elements based on poly-Si TFT or MIM.

A significant difference between the displays according to the invention and those previously used on the basis of the twisted nematic cell, however, is the choice of the liquid crystal parameters of the liquid crystal layer.

The liquid crystal mixtures which can be used according to the invention are prepared in a manner which is conventional per se. As a rule, the desired amount of the components used in smaller amounts is dissolved in the components which make up the main constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent after thorough mixing, for example by distillation.

The dielectrics can also contain further additives known to the person skilled in the art and described in the literature. For example, 0-15% pleochroic dyes or chiral dopants can be added.

, wobei ε_∥ die Dielektrizitätskonstante parallel zu den Moleküllängsachsen und ε_⊥ die Dielektrizitätskonstante senkrecht dazu bedeutet. Die elektrooptischen Daten wurden in einer TN-Zelle im 1. Minimum (d.h. bei einem d . Δn-Wert von 0,5) bei 20 °C gemessen, sofern nicht ausdrücklich etwas anderes angegeben wird. Die optischen Daten wurden bei 20 °C gemessen, sofern nicht ausdrücklich etwas anderes angegeben wird.C means a crystalline, S a smectic, S _B a smectic B, N a nematic and I the isotropic phase. V₁₀ denotes the voltage for 10% transmission (viewing direction perpendicular to the plate surface). t _on denotes the switch-on time and t _off the switch-off time at an operating voltage corresponding to 2.5 times the value of V₁₀. An denotes the optical anisotropy and n _o the refractive index. Δε denotes the dielectric anisotropy ${\text{(Δε = ε}}_{\text{∥}}{\text{- ε}}_{\text{⊥}}\text{)}$

, where ε _∥ the dielectric constant parallel to the _{longitudinal axes of} the molecules and ε _⊥ the dielectric constant perpendicular to it. The electro-optical data were measured in a TN cell at the 1st minimum (ie at a Δn value of 0.5) at 20 ° C., unless expressly stated otherwise. The optical data were measured at 20 ° C, unless expressly stated otherwise.

The following examples are intended to illustrate the invention without limiting it. All temperatures above and below are given in ° C. The percentages are percentages by weight.

In the present application and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, the transformation into chemical formulas taking place according to Tables A and B below. All radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals with n or m C atoms. The coding according to Table B goes without saying. In Table A, only the acronym for the base body is given. In individual cases, a code for the substituents R¹, R², L¹ and L² follows separately from the acronym for the basic body: Code for R¹, R², L¹, L² _, R¹ R² L¹ L² nm C _n H _{2n + 1} C _m H _{2m + 1} H H no C _n H _{2n + 1} OC _m H _{2m + 1} H H nO.m OC _n H _{2n + 1} C _m H _{2m + 1} H H n C _n H _{2n + 1} CN H H nN.F C _n H _{2n + 1} CN H F nF C _n H _{2n + 1} F H H nOF OC _n H _{2n + 1} F H H nCl C _n H _{2n + 1} Cl H H nF.F C _n H _{2n + 1} F H F nOmFF C _n H _{2n + 1} OC _m H _{2m + 1} F F nmF C _n H _{2n + 1} C _m H _{2m + 1} F H nCF₃ C _n H _{2n + 1} CF₃ H H nOCF₃ C _n H _{2n + 1} OCF₃ H H nOCF₂ C _n H _{2n + 1} OCHF₂ H H nS C _n H _{2n + 1} NCS H H rVsN C _r H _{2r + 1} -CH = CH-C _s H _2s - CN H H rEsN C _r H _{2r + 1} -OC _s H _2s - CN H H nNF C _n H _{2n + 1} CN F H n C _n H _{2n + 1} COOC _m H _{2m + 1} H H

In addition to one or more compounds according to the invention, the liquid-crystalline media according to the invention preferably contain 2 to 40, in particular 4 to 30, components as further constituents. These media very particularly preferably contain 7 to 25 components in addition to one or more compounds according to the invention. These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular substances from the classes of the biphenyls, terphenyls, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclobhexene, 1,4-cyclobenzene, 1,4-cyclobenzene, 1,4-cyclobenzene, 1,4-cyclobenzene, '-Bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithiane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1- Cyclohexyl-2 (4-phenyl-cyclohexyl) ethane, 1-cyclohexyl-2-biphenylylethane, 1-phenyl-2-cyclohexylphenylethane and tolane. The 1,4-phenylene groups in these compounds can also be fluorinated.

The most important compounds which are suitable as further constituents of media according to the invention can be characterized by the formulas 1, 2 and 3:



R'-LE-R '' 1





R'-L-CH₂CH₂-E-R '' 2





R'-LC≡CE-R '' 3



In formulas 1, 2 and 3, L and E, which may be the same or different, each independently represent a bivalent radical from the group consisting of -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, - Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- as well as their Mirror images formed group, where Phe unsubstituted or substituted by fluorine-1,4-phenylene, Cyc trans-1,4-cyclohexylene or 1,4-cyclohexenylene, pyr pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio 1,3-dioxane-2,5-diyl and G 2- (trans-1,4-cyclohexyl) ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2 , 5-diyl mean.

One of the radicals L and E is preferably Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably contain one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which L and E are selected from the group Cyc, Phe and Pyr and at the same time one or more components selected from the compounds of Formulas 1, 2, 3, 4 and 5, in which one of the radicals L and E is selected from the group Cyc, Phe and Pyr and the other radical is selected from the group -Phe-Phe-, -Phe-Cyc-, - Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or more components selected from the compounds of the formulas 1, 2, 3, 4 and 5, in which the radicals L and E are selected from the group -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

In the compounds of the sub-formulas 1a, 2a and 3a, R 'and R''each independently represent alkyl, alkenyl, alkoxy, alkenyloxy or alkanoyloxy having up to 8 carbon atoms. In most of these compounds, R 'and R''are different from one another, one of these radicals usually being alkyl or alkenyl. In the compounds of sub-formulas 1b, 2b and 3b, R '' is OCF₃, -CF₃, OCHF₂, F, Cl or -NCS; R has the meaning given for the compounds of partial formulas 1a to 3a and is preferably alkyl or alkenyl. However, other variants of the proposed substituents in the compounds of the formulas 1, 2 and 3 are also common. Many such substances or mixtures thereof are commercially available. All of these substances can be obtained by methods known from the literature or by analogy.

Gruppe 1:

20 bis 90 %, insbesondere 30 bis 90 %,

Gruppe 2:

10 bis 80 %, insbesondere 10 bis 50 %,

wobei die Summe der Anteile der erfindungsgemäßen Verbindungen und der Verbindungen aus den Gruppen 1 und 2 bis zu 100 % ergeben. Besonders bevorzugt sind Medien, die neben erfindungsgemäßen Verbindungen nur Komponenten aus der Gruppe 2 enthalten.In addition to components from the group of compounds 1a, 2a and 3a (group 1), the media according to the invention can also contain components from the group of compounds 1b, 2b and 3b (group 2), the proportions of which are preferably as follows:

Group 1:

20 to 90%, in particular 30 to 90%,

Group 2:

10 to 80%, in particular 10 to 50%,

the sum of the proportions of the compounds according to the invention and of the compounds from groups 1 and 2 giving up to 100%. Media which contain only components from group 2 in addition to compounds according to the invention are particularly preferred.

The media according to the invention preferably contain 1 to 40%, particularly preferably 5 to 30%, of compounds according to the invention. Also preferred are media containing more than 40%, in particular 45 to 90%, of compounds according to the invention. The media preferably contain three, four or five compounds according to the invention.

The construction of the MFK display according to the invention from polarizers, electrode base plates and electrodes with surface treatment corresponds to the design customary for such displays. Here the term conventional construction is broadly encompassed here and also encompasses all modifications and modifications of the MLC display, in particular also matrix display elements based on poly-Si TFT or MIM.

A major difference between the displays according to the invention and the conventional ones based on the twisted nematic cell, however, is the choice of the liquid crystal parameters of the liquid crystal layer.

The liquid crystal mixtures which can be used according to the invention are prepared in a manner which is conventional per se. As a rule, the desired amount of the components used in smaller amounts is dissolved in the components which make up the main constituent, advantageously at elevated temperature. It is also possible to use solutions of the components in an organic solvent, e.g. in acetone, chloroform or methanol, and to remove the solvent after mixing, for example by distillation.

The dielectrics can also contain further additives known to the person skilled in the art and described in the literature. For example, 0-15% pleochroic dyes or chiral dopants can be added.

, wobei ε_∥ die Dielektrizitätskonstante parallel zu den Moleküllängsachsen und ε_⊥ die Dielektrizitätskonstante senkrecht dazu bedeutet. Die elektrooptischen Daten wurden in einer TN-Zelle mit einem Plattenabstand von 6 »m bei 20 °C gemessen, sofern nicht ausdrücklich etwas anderes angegeben wird. Die optischen Daten wurden bei 20 °C gemessen, sofern nicht ausdrücklich etwas anderes angegeben wird. V_th ist die Schwellenspannung V_(10,0,20) in Volt.C means a crystalline, S a smectic, S _B a smectic B, H a nematic and I the isotropic phase. T _c is the clearing point NI in ° C. η is the flow viscosity in mPa.s. V₁₀ denotes the voltage for 10% transmission (viewing direction perpendicular to the plate surface). t _on denotes the switch-on time and t _off the switch-off time for an operating voltage corresponding to 2.5 times the value of V₁₀. Δn denotes the optical anisotropy (589 nm, 20 ° C) and n _o the refractive index. Δε denotes the dielectric anisotropy ${\text{(Δε = ε}}_{\text{∥}}{\text{- ε}}_{\text{⊥}}\text{)}$

, where ε _∥ the dielectric constant parallel to the _{longitudinal axes of} the molecules and ε _⊥ the dielectric constant perpendicular to it. The electro-optical data were measured in a TN cell with a plate spacing of 6 »m at 20 ° C, unless expressly stated otherwise. The optical data were measured at 20 ° C, unless expressly stated otherwise. V _th is the threshold voltage V _(10,0,20) in volts.

The following examples are intended to illustrate the invention without limiting it. All temperatures above and below are given in ° C. The percentages are percentages by weight.

example 1

PDX-3F 15% PDX-5F 13% PYP-5F 13% CCP-20CF₃ 8th % CCP-30CF₃ 13% CCP-40CF₃ 5% CCP-50CF₃ 12% ECCP-3F.F 13% ECCP-30CF₃ 8th %

Example 2

PDX-3Cl 10% PDX-3F.F 11% PCH-5F 14% CCP-20CF₃ 11% CCP-30CF₃ 14% CCP-40CF₃ 7% CCP-50CF₃ 12% ECCP-3F.F 13% ECCP-30CF₃ 8th %

Example 3

PDX-5F 15.5 Clearing point [° C] 65.5 PCH-5F 14.6 Δn (589 nm, 20 ° C) 0.0868 CCP-20CF₃ 7.8 n _e (589 nm, 20 ° C) 1.5675 CCP-30CF₃ 12.6 V _(10.0.20) 1.66 CCP-40CF₃ 4.8 CCP-50CF₃ 11.6 BCH-3F.F 11.6 BCH-5F.F 13.6 ECCP-2F.F 7.8

Example 4

PDX-5F.F 16.0 Clearing point [° C] 64.2 PCH-5F 12.0 Δn (589 nm, 20 ° C) 0.0774 CCP-20CF₃ 8.0 n _e (589 nm, 20 ° C) 1.5689 CCP-30CF₃ 13.0 V _(10.0.20) 1.50 CCP-40CF₃ 5.0 CCP-50CF₃ 12.0 BCH-3F.F 12.0 BCH-5F.F 14.0 ECCP-2F.F 8.0

Example 5

PDX-3CL.F 16.0 Clearing point [° C} 66.6 PCH-5F 12.0 Δn (589 nm, 20 ° C) 0.0934 CCP-20CF₃ 8.0 n _e (589 nm, 20 ° C) 1.4819 CCP-30CF₃ 13.0 V _(10.0.20) 1.46 CCP-40CF₃ 5.0 CCP-50CF₃ 12.0 BCH-3F.F 12.0 BCH-5F.F 14.0 ECCP-2F.F 8.0

Example 6

PDX-5F.F 16.3 Clearing point [° C] 66.4 PDX-5F 10.2 Δn (589 nm, 20 ° C) 0.0886 CCP-20CF₃ 8.2 n _e (589 nm, 20 ° C) 1.5671 CCP-30CF₃ 13.3 V _(10.0.20) 1.56 CCP-40CF₃ 5.1 CCP-50CF₃ 12.2 BCH-3F.F 12.2 BCH-5F.F 14.3 ECCP-2F.F 8.2

Example 7

PDX-5F.F 10.0 Clearing point [° C] 91.3 PDX-5F 10.0 Viscosity [mm²s ^-1] 20 ° 16.8 PCH-7F 10.0 Δn (589 nm, 20 ° C) 0.0840 CCP-30CF₃ 13.0 n _e (589 nm, 20 ° C) 1.5615 CCP-50CF₃ 12.0 Δε (1 kHz, 20 ° C) 5.6 ECCP-30CF₃ 10.0 ε _∥ (1 kHz, 20 ° C) 9.3 ECCP-3F.F 13.0 V _(10.0.20) 2.11 ECCP-5F.F 10.0 CBC-33 4.0 CBC-53F 4.0 CBC-55F 4.0

Example 8

PYP-30CF₃ 15% PYP-50CF₃ 13% PYRP-30CF₃ 13% CCP-20CF₃ 8th % CCP-30CF₃ 13% CCP-40CF₃ 5% CCP-50CF₃ 12% ECCP-3F.F 13% ECCP-30CF₃ 8th %

Example 9

PYRP-30CF₃ 10% PYRP-50CF₃ 11% PCH-5F 14% CCP-20CF₃ 11% CCP-30CF₃ 14% CCP-40CF₃ 7% CCP-50CF₃ 12% ECCP-3F.F 13% ECCP-30CF₃ 8th %

Example 10

PYRP-30CF₃ 15% PYRP-3F 13% PYRP-5F.F 13% CCP-20CF₃ 8th % CCP-30CF₃ 13% CCP-40CF₃ 5% CCP-50CF₃ 12% ECCP-3F.F 13% ECCP-30CF₃ 8th %

Example 11

PYRP-5CF₃ 15% PCH-5F 13% PYRP-5F.F 13% CCP-20CF₃ 8th % CCP-30CF₃ 13% CCP-40CF₃ 5% CCP-50CF₃ 12% ECCP-3F.F 13% ECCP-30CF₃ 8th %

Example 12

PDX-5F 10% T _c : 91 ° C PCH-7F 10% Δn: 0.084 PDX-5F.F 10% V _th : 2.11 CCP-30CF₃ 13% η: 17th CCP-50CF₃ 12% ECCP-30CF₃ 10% ECCP-3F.F 13% ECCP-5F.F 10% CBC-33 4% CBC-53F 4% CBC-55F 4%

Example 13

PDX-5F.F 16% T _c : 64 ° C PCH-5F 12% Δn: 0.077 CCP-20CF₃ 8th % V _th : 1.50 CCP-30CF₃ 13% CCP-40CF₃ 5% CCP-50CF₃ 12% BCH-3F.F 12% BCH-5F.F 14% ECCP-2F.F 8th %

Example 14

PDX-5F 12% T _c : 91 ° C PDX-7F 10% Δn: 0.096 PCH-7F 5% V _th : 1.93 CCP-30CF₃ 11% CCP-50CF₃ 11% ECCP-3F.F 12% ECCP-30CF₃ 11% BCH-3F.F 10% BCH-5F.F 9% CBC-33F 3% CBC-53F 3% CBC-55F 3%

Example 15

PDX-5F.F 10% T _c : 86 ° C PDX-5F 10% Δn: 0.085 PCH-5Cl 10% V _th : 2.1 CCP-3F.F 13% CCP-5F.F 12% ECCP-30CF₃ 10% ECCP-3F.F 13% ECCP-5F.F 10% CBC-33 4% CBC-53F 4% CBC-55F 4%

Example 16

PDX-5F.F 10% T _c : 70 ° C PCH-6F 6% Δn: 0.085 PCH-7F 15% V _th : 1.7 V CCP-20CF₃ 10% CCP-30CF₃ 11% CCP-50CF₃ 12% BCH-3F.F 13% BCH-5F.F 13% CP-3Cl.F 10%

Example 17

PDX-5F.F 9% T _c : 74 ° C PCH-6F 7% Δn: 0.08 PCH-7F 7% V _th : 1.7 V CCP-20CF₃ 10% CCP-30CF₃ 12% CCP-40CF₃ 9% CCP-50CF₃ 12% BCH-3F.F 6% ECCP-3F.F 8th % ECCP-5F.F 6% BCH-3F.F.F 14%

Example 18

PCH-7F 7% T _c : 79 ° C PCH-5F 9% Δn: 0.09 PYRP-30CF₃ 3% V _th : 1.7 V PYRP-50CF₃ 4% CCP-20CF₃ 10% CCP-30CF₃ 12% CCP-40CF₃ 9% CCP-50CF₃ 12% BCH-3F.F 6% ECCP-3F.F 8th % ECCP-5F.F 6% BCH-3F.F.F 14%

Example 19

PYRP-30CF₃ 5% T _c : 78 ° C PYRP-50CF₃ 5% Δn: 0.09 PCH-6F 6% V _th : 1.7 V PCH-5F 15% CCP-20CF₃ 10% CCP-30CF₃ 11% CCP-50CF₃ 12% BCH-3F.F 13% BCH-5F.F 13% CP-3Cl.F 10%

Example 20

A basic mixture M _o consists of ECCP-3Cl 23% ECCP-5Cl 33% ECCP-5Cl.F 24% PCH-6F 20%

The mixtures M₁ and M₂ according to the invention consist of 90% Mo and 10% PDX-3Cl (M₁) or 10% PYRP-1cl (M₂) Physical parameters of this mixture: the following table. M _o M₁ M₂ T _c 114 100 103.5 Δn 0.0946 0.0936 0.1087 V _th (90 ° TN cell) 3.79 3.23 3.20 V _sat 5.14 4.57 4.48

Example 21

PDX-3F 10% T _c : -88 ° C PDX-5F 8th % η: 22 PDX-7F 6% Δε: +61 CCP-20CF₃ 8th % Δn: 0.091 CCP-30CF₃ 10% CCP-40CF₃ 7% CCP-50CF₃ 10% BCH-3F.F.F 12% BCH-5F.F.F 10% ECCP-30CF₃ 5% ECCP-50CF₃ 5% CBC-33F 3% CBC-53F 3% CBC-55F 3%

Example 22

PDX-3F 10% T _c : +89 ° C PDX-5F 8th % η: 22 PDX-7F 6% Δε: +6.0 CCP-30CF₃ 11% Δn: 0.092 CCP-40CF₃ 6% CCP-50CF₃ 10% CCP-3F.F.F 10% BCH-3F.F 12% BCH-5F.F 10% ECCP-30CF₃ 5% ECCP-50CF₃ 5% CBC-33F 2% CBC-53F 2% CBC-55F 2%

Example 27

PCH-6F 6% T _c : 84 ° C PCH-JF 5% Δn: 0.127 PYP-5F 5% V _th : 2.25 (2 ^nd minimum) CCP-30CF₃ 15% CCP-50CF₃ 13% ECCP-3F.F 4% BCH-3F.F 18% BCH-5F.F 14% BEP-3Cl.F 10% BEP-5Cl.F 10%

Example 28

PCH-6F 6% T _c : 84 ° C PYP-3Cl.F 5% Δn: 0.131 PYP-5F 5% V _th : 2.2 (2 ^nd minimum) CCP-30CF₃ 15% CCP-50CF₃ 13% ECCP-3F.F 4% BCH-3F.F 18% BCH-5F.F 14% BEP-3Cl.F 10% BEP-5Cl.F 10%

Claims (8)

1. Liquid-crystalline media based on a mixture of medium-polarity compounds, characterized in that it contains one or more compounds of the general formula I

   

   in which the individual radicals have the following meanings:

   R   is alkyl, oxaalkyl, fluoroalkyl or alkenyl, in each case having up to 7 carbon atoms,

   

   X   is F, Cl, OCHF₂, OCF₂Cl or OCF₃, and

   Y   is H or F,

   and additionally contains one or more compounds selected from the group consisting of the general formulae II, III and IV and/or V to VIII:

   

   

      in which R, X and Y are each, independently of one another, as defined for formula I, media comprising compounds of the formula

   

      in which R¹ and R² are each, independently of one another, n-alkyl, ω-fluoroalkyl or n-alkenyl having up to 9 carbon atoms being excluded.
2. Medium according to Claim 1, characterized in that it additionally contains one or more compounds selected from the group consisting of the general formulae IX to XII:

   

      in which R, X and Y are each, independently of one another, as defined in Claim 1.
3. Medium according to Claim 1, characterized in that the proportion of compounds of the formulae I to IV together is at least 50% by weight in the total mixture.
4. Medium according to Claim 1 or 2, characterized in that the proportion of compounds of the formula I is from 10 to 50% by weight in the total mixture.
5. Medium according to at least one of Claims 2 to 4, characterized in that the proportion of compounds of the formulae II to IV is from 40 to 90% by weight in the total mixture.
6. Medium according to at least one of Claims 1 to 4, characterized in that it essentially comprises compounds selected from the group consisting of the general formulae I to XII.
7. Use of the liquid-crystalline medium according to Claim 1 for electrooptical purposes.
8. Electrooptical liquid-crystal display containing a liquid-crystalline medium according to Claim 1.